The present invention relates to a stack control mechanism for sheets of paper and more particularly to an improved means for controlling the height of a stack of paper sheets.
Sheets of paper are assembled in a stack in an accumulating area by a sheet feeding mechanism. After a predetermined number of sheets have been deposited into the accumulating area they are then fed out of the accumulating area one by one. When the stack reaches a certain height, the feeding into the accumulating area is stopped and when the height of the stack falls below a certain level, the feeding resumes. In current sheet feeding mechanisms, mechanical devices are used in conjunction with mechanical limit switches to detect paper stack height. As each sheet enters the accumulating area, the sheet is driven through and under a mechanical lever before it stops against a singulating roller.
With the recent use of lighter weight papers used for printing processes, the thickness of the traditional sheet has been reduced to the lower end of the standard. Hence, sheets of paper have less over all strength so that the rigidity of the papers is reduced. This results in paper buckling and if the sheets are interfered with by a mechanical sensing mechanism uneven shingling and irregular and double sheet feeding results. In addition, it has been found that print smudging of the sheets sometimes occurs in the singulation area. Controlling the stack height and keeping the paper to a minimum amount of sheets allows for lighter contact with the high friction surfaces of the singulation roller and the singulation indexing belt that the sheet is subjected to as it is pulled through and singulated from the stack. The stack weight resistance in combination with the high friction surfaces is one of the major causes of print smudging in mechanical feed devices in printing processes. In addition, presently used stack control mechanisms are complex to use and expensive and complex to manufacture and maintain.
The present invention eliminates these drawbacks and has as one of its objects the provision of an improved stack control mechanism
Another object of the present invention is the provision of an improved stack control mechanism in which the height of the stack is easily controlled.
Another object of the present invention is the provision of an improved stack control mechanism in which the height of the stack is controlled without the use of any mechanical means touching the sheets being accumulated.
Another object of the present invention is the provision of an improved stack control mechanism in which the number of sheets accumulated in the accumulating area are reduced to a minimum.
Another object of the present invention is the provision of an improved stack control mechanism which eliminates any smudging of printing on the sheets.
Another object of the present invention is the provision of a improved stack control mechanism which is simple to use.
Another object of the present invention is the provision of an improved stack control mechanism which is inexpensive and simple to manufacture and maintain.
Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to described, or will be indicated in the appended claims and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.